1. Field of the Invention
The present invention relates to a process for producing an optical article with an anti-reflection film. The process of the present invention can be preferably used to endow an optical article such as plastic lens or the like with an anti-reflection property.
2. Description of the Prior Art
In plastic lenses with an anti-reflection film, the film has been formed using a method such as vapor deposition, ion sputtering or the like. As compared with inorganic glass lenses with an anti-reflection film, plastic lenses with an anti-reflection film have had problems in that the base material (plastic lens) and the anti-reflection film are largely different in expansion coefficient and moreover low in adhesion to each other. The plastic lenses with an anti-reflection film have had a further problem in that when an anti-reflection film of inorganic substance is formed on a plastic lens according to, for example, a vapor deposition method, a high vacuum and a long production time are required, making the productivity and economy insufficient.
Hence, as a method replacing the vacuum deposition method or the ion sputtering method, there was developed a coating method wherein a liquid coating composition containing, as film-forming components, an inorganic compound (e.g. colloidal silica) or an organic compound (e.g. organic silicon compound) is coated on a plastic lens and then the resulting lens is heated to form an anti-reflection film thereon. For instance, Japanese Patent Application Kokai (Laid-Open) No. 23036/1985 discloses a method for forming a two-layer anti-reflection film on a plastic lens using two liquid organic coating compositions each containing, as a film-forming component, a glycidoxyalkyltrialkoxysilane or its hydrolyzate, wherein the coating composition for the first layer film further contains a titanium compound (e.g. titanium tetraalkoxide) and an organic carboxylic acid (e.g. acetic acid) in order to provide an anti-reflection film of superior tintability and staining resistance.
The plastic lenses with an anti-reflection film obtained by coating liquid coating compositions in two layers according to, for example, the above method of Japanese Patent Application Kokai (Laid-Open) No. 23036/1985, as compared with those obtained according to the vapor deposition method, are superior in heat resistance, tintability by disperse dye, etc. but inferior in scratching resistance of anti-reflection film, giving rise to the peeling of the anti-reflection film. This reduction in scratching resistance in the plastic lenses with an anti-reflection film obtained according to the coating method is particularly striking, for example, when the lenses have been subjected to a tinting treatment or to high temperature-high humidity conditions for a long period of time, and in such cases, there also occur an undesirable problem of change of interference color due to the shift of wavelength at minimum reflectivity in a visible light range. This phenomenon is attributed to the film-forming components, particularly the titanium tetrabutoxide which is the high refractive index component of the first layer film. This component is rapidly hydrolyzed by water or humid air and simulataneously is condensed and accordingly, when allowed to stand in an atmosphere of controlled humidity, forms a colorless and transparent film having a structure close to titanium oxide. However, unless the drying or curing of the first layer film contaning an organic silance compound and the above mentioned titanium tetrabutoxide is conducted under an appropriately controlled (increased) humidity, unreacted components remain in the film and, after the formation of an anti-reflection film, these unreacted components cause the above mentioned problem when subjected to a hot water treatment, etc. Further, the water-repellent and smooth surface of the first layer film makes low the adhesivity of the second layer film to the first layer film.
In order to solve these problems, it is known that the first layer film is dried and/or cured at an elevated temperature and under an increased humidity and further the first layer film is subjected to a plasma treatment to enhance the adhesivity between the first layer film and the second layer film. It is also known that an undercoat is formed between the base material (plastic lens) and the anti-reflection film to improve the scratching resistance of the anti-reflection film. However, these approaches require a special operational technique (e.g. plasma treatment, chemical treatment) and invite new problems such as increase in process steps and resulting possibility of increased contamination with foreign matters.
Hence, the first object of the present invention is to provide an optical article with a two-layer anti-reflection film having excellent adhesivity between the first layer film and the second layer film without subjecting the first layer film to a surface treatment.
The second object of the present invention is to provide an optical article with a two-layer anti-reflection film having excellent scratching resistance without using an undercoat between the base material and the film.
The third object of the present invention is to provide an optical article with a two-layer anti-reflection film whose scratching resistance and adhesivity to the base material remain unchanged even after having been subjected to a tinting treatment or to severe conditions (e.g. high temperature-high humidity conditions).
The other objects of the present invention will be apparent from the following description.